﻿// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'

// 单张纹理
Shader "Custom/Chapter 7/SingleTexture" {
	Properties {
		_Color ("Color", Color) = (1,1,1,1)
		_MainTex ("Main Tex", 2D) = "white" {}
		_Specular ("Specular",Color) = (1,1,1,1)
		_Gloss ("Gloss",Range(8.0,256)) = 20
	}
	SubShader {
		Pass {
			Tags { "LightMode"="ForwardBase" }
		
			CGPROGRAM

			#pragma vertex vert
			#pragma fragment frag

			#include "Lighting.cginc"

			fixed4 _Color;
			sampler2D _MainTex;
			float4 _MainTex_ST;		// S:scale, T:translation, _MainTex_ST.xy:缩放值, _MainTex_ST.zw:偏移值
			fixed4 _Specular;
			float _Gloss;

			struct a2v {
				float4 vertex : POSITION;
				float3 normal : NORMAL;
				float4 texcoord : TEXCOORD0;			// 第一组纹理
			};

			struct v2f {
				float4 pos : SV_POSITION;
				float3 worldNormal : TEXCOORD0;
				float3 worldPos : TEXCOORD1;
				float2 uv : TEXCOORD2;					// 存储纹理坐标
			};

			v2f vert(a2v v) {
				v2f o;
				o.pos = UnityObjectToClipPos(v.vertex);
				o.worldNormal = UnityObjectToWorldNormal(v.normal);
				o.worldPos = mul(unity_ObjectToWorld,v.vertex).xyz;

				o.uv = v.texcoord.xy * _MainTex_ST.xy + _MainTex_ST.zw;
				// 变换纹理，同下，下面是内置函数
				// o.uv = TRANSFORM_TEX(v.texcoord,_MainTex);
				return o;
			}

			fixed4 frag(v2f i) : SV_TARGET {
				fixed3 worldNormal = normalize(i.worldNormal);
				fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));

				fixed3 albedo = tex2D(_MainTex,i.uv).rgb * _Color.rgb;		// 获取纹理和其坐标计算纹理值，乘于颜色，作为反射率
				fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz * albedo;		// 反射率和环境光相乘得到环境光部分
				fixed3 diffuse = _LightColor0.rbg * albedo * max(0,dot(worldNormal,worldLightDir));	// 漫反射公式

				fixed3 viewDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
				fixed3 halfDir = normalize(worldLightDir + viewDir);
				fixed3 specular = _LightColor0.rgb * _Specular.rgb * pow(max(0,dot(worldNormal,halfDir)),_Gloss);
				return fixed4(ambient + diffuse + specular,1.0);
			}

			ENDCG
		}
	}
	FallBack "Specular"
}
